Certainly, from a literary viewpoint,
the writing style is somewhat poor, for the very same reasons mentioned
above. But when it comes to using a software manual, which do you prefer?

More suitable brightness levels
may be achieved using the brightness and contrast settings and progressively
increasing or decreasing the value of the brightness level of each separate
color channel, namely Red, Green and Blue - or Cyan, Magenta, Yellow,
Black - or that of the combined channels, which can be accessed by expanding
the "picture" menu and selecting "brightness and contrast".

Or

To optimize the brightness and contrast
level, go to "Picture/Brightness and contrast". In the dialog,
select the channels - or combined channels - you want to adjust:

Red

Green

Blue

RGB

or,

Cyan

Magenta

Yellow

Black

CMYK

and modify progressively the channels' values.

As an user, which instructions would you rather follow?

(This is a bogus example, no a real
manual excerpt, but I think it makes the point)

Simplified English is not only easier
to grasp, but it is also shorter in size (In the above example, almost
30% shorter.) cutting
down to the same degree the translation costs!

Controlled English

Simplified English is actually a basic
form of Controlled English. The fundamental idea is pretty
much the same. If you force in rules at the time of the writing, the documents
will be easier to understand and consistency will increase. It was meant
to create documents that could be then processed by machine translation.

At that time, machine translation was
definitely not an option - and it still isn't - due to the complexity
of human languages, passive forms, colloquialisms, metaphors, terminology...
and it was clear that it wouldn't be within reach for a long time.